Ultrafast coherent control of molecular dynamics with shaped laser pulses

点击翻译按钮获取中文摘要

Our research is focused on controlling molecular dynamics with high-power ultra-short laser pulses. Specifically, we develop new methods of exciting extreme rotational states – the so called “molecular super rotors”, and investigate the effects of ultra-fast rotation on chemical and physical properties of isolated molecules, molecular clusters and dense molecular gases. Control of molecular rotation has been long recognized and successfully used as a powerful tool for steering chemical reactions, imaging individual molecular orbitals, generating attosecond laser pulses and separating molecular isotopes. Recent theoretical studies have indicated enormous potential in extending the reach of rotational control to ultra-high rotational states. Ultrafast molecular spinning has been predicted to change the character of molecular collisions with solid surfaces and alter molecular trajectories in external fields. New ways of molecular cooling and selective chemical bond breaking by inducing super rotation have been suggested. Yet, owing to multiple technological challenges, no research on molecular super rotors is currently pursued in Canada. In a series of recent works, our research team has successfully demonstrated new approaches to controlling molecular rotation. We have built an “optical centrifuge” and succeeded in producing, observing and controlling molecular super rotors. We also develop a method of exciting extreme rotational states with high-power ultra-short pulse trains. The two methods are complementary and offer different schemes of rotational control. We intend to explore the following unique aspects of molecular science at the limit of extreme rotational speed. (1) Effects of centrifugal distortion and the possibility of selective chemical bond breaking by means of controlled ultrafast molecular spinning; (2) Rotation-induced magnetic properties of diamagnetic and paramagnetic super rotors, including the behaviour of centrifuged molecules in external magnetic field; (3) Rotation-induced electrical properties of polar super rotors, including the possibility for new sources of THz radiation; (4) Dependence of molecule-surface scattering on the orientation and magnitude of the molecular angular momentum; (5) Effects of molecular rotation on superfluidity of helium nanodroplets; (6) Control of quantum molecular rotation in the regime of classically chaotic dynamics; (7) Collisional properties of molecular super rotors and the aspects of rotational energy transfer from isolated molecular rotation to collective gas vortices; (8) Prospects of controlling chemical reactions by tuning molecular rotation in the extreme range of angular frequencies. Similarly to other exotic states of matter, such as ultra-cold atoms or anti-matter, super rotors will provide new insights into the fundamental laws of nature beyond currently established boundaries. We plan to investigate super rotation of hydrogen, nitrogen, oxygen and carbon dioxide - some of the nature’s most fundamental building blocks. The uniqueness of super rotors suggests an immediate impact on general science, and far-reaching effects on modern technology. From a chemistry viewpoint, the effect of ultrafast molecular rotation on chemical reactions begs detailed investigation. From the perspective of physics, we anticipate to find out new electrical, magnetic and optical properties of super rotors. For astronomy, the analysis of extremely hot gases around stars may benefit from the spectroscopy of ultrafast rotating molecules accessible in table-top laboratory experiments. In nano-science, the effects of super rotation on nano-deposition and molecule-surface scattering are of practical interest.